Ring counter utilizing bipolar field-effect devices



Nov. 26, 1963 Filed May 2,

c. R. cooK, JR., x-:TAL 3,112,411

RING COUNTER UTILIZING BIPOLAR FIELD-EFFECT DEVICES 1960 3 Sheets-She'eb 1 Nov. 26, 1963 Q R, COOK, JR., ETAL 3,112,411

RING COUNTER UTILIZING BIPOLAR FIELD-EFFECT DEVICES Filed May 2, 1960 3 Sheets-Sheet 2 ai M' IN V EN TOR' ATTORNEYS Nov. 26, 1963 RING COUNTER UTILIZING BIPOLAR FIELD-EFFECT DEVICES Filed May 2. 1960 C. R. COOK, JR., ETAL 3 Sheets-Sheet 5 l SQ I Il. I

IN V EN TOR-- ATTORNEYS 3,112,411 RING CUNTER UTILIIZING BHZPULAR FELD-EFFECT DEVLCES Charles R. Cook, 1r., and Geraid Lueclte, Richardson, Tex., assigner-s to Texas Instruments Incorporated, Dalias, Tex., a corporation of Delaware Filed May 2, 1961i, Ser. No. 26,0% Claims. (Cl. 367-885) Ring counters involving bistable circuits including those making use oi semiconductor 4active circuit elements are well known. The ring counter of the present invention is a semiconductor circuit, and :as such has the kgeneral advautages of semiconductor circuits, vbeing of light weight, having low power consumption, and taking up a small amount of space. The ring counter of the present invention is superior to the semiconductor ring counters of the prior art because it uses a field-effect device as its active circuit element. The field-eilect device has a high-input impedance, both when it is being turned on and when it is being turned ott. As a result, the ring counter of the present invention has less complicated circuitry and requires less trigger power than the semiconductor ring counter circuits of the prior art.

Furthermore, the ring counter of the present invention makes use of a single active circuit element in each stage whereas semiconductor ring counter circuits of the prior art of comparable quality require at least two active circuit elements.

Further objects and advantages of che present invention become apparent as the following detailed ydescription unfolds, Kand when taken in conjunction with the drawings wherein:

FiGURE 1 illustrates a -unipolar field-effect transistor;

FIGURE 2a illustrates -a bipolar held-effect transistor of the type made use of in the present invention;

FIGURE 2b is the top view of a preferred yform of the bipolar iield-elect transistor;

FIGURE 2c is a cross sectional View through FIG- URE 2b;

FIGURE 3 illustrates the equivalent circuit of the bipolar held-effect transistor;

FIGURE 4 illustrates a characteristic of the bipolar field-effect transistor;

FIGURE 5 is an illustration of a circuit exemplifying the switching properties of the bipolar field-effect transistor;

FIGURE 6 is a schematic illustration of the ring counter of the present invention;

FIGURE 7 is the plan view of :a semiconductor network providing the circuitry for a single stage of the ring counter of the present invention; and

FIGURE 8 is a cross-sectional view through FG- URE 7.

The present invention makes use of a bipolar field-effect transistor which is a m'odiication of a unipolar fieldeitect transistor such as that illustrated in FIGURE 1. The unipolar ieldaettect transistor in FIGURE l coinprises a block 11 of N-type material in which is formed a diffused slayer 12 of P-type material lforming a PN juno tion 13 with the N-type material of the block 11. In the middle of the layer 12 of P-type material is a diiused section 14 of N-type material which extends down into the layer 12 of P-type material, dividing it into two main parts 12a and 12b connected by a narrow conducting channel 15 of P-type material bounded by the N-type material of block I11 and the `section 14 of N-type material. The section 14 of N-type material makes a PN junction 16 with the layer 12 of P-type material. An ohmic connection is made to one of the main parts 12u of the layer 12 of P-type material. This connection provides the source 17 of the iield-eiect transistor. An

ate t ohrnic connection is made lto the other main part 12b of the layer 12 of P-type material to provide the drain 18 of the eld-eifect transistor. Ohmic connections are also made to the section 14 and to the block 11 `on the side opposite to the :layer 12, which connections are connected together to form the gate 19 of the field-edect transistor.

The width of the channel 15 between the boundaries provided -by the PN junctions 13 and 16 is important in determining the characteristics of the iield-eiect transistor. This Width is controlled and determined by the depths of diffusion of the layer 12 and the section 14. With this structure, the conductance in the channel 15 of P-type material between the source 17 and the drain 18 is controlled by the voltage applied to the gate 19.

FIGURE 2a illustrates a bipolar field-eect transistor of the type which is used in the circuit of the present invention. As shown in FIGURE 2a, the bipolar eldeffect transistor, like the unipolar ield-elect transistor illustrated in FIGURE l, `comprises a block 11 of N-type material on which there is a diffused layer 12 of P-type material. in the layer 12 is `a diffused section 1li of N-type material. The N-type material of the block 11 forms a PN junction 13 with the layer 12 of P-type material. The section 14 of N-type material also forms a PN junction 16 with the layer 12 of Petype material. As in the unipolar transistor, the section 14- extends into the layer 12, dividing it into two major parts 12a `and 12b connected -by -a narrow channel 15 of P-type material. An ohmic contact is made with the part 12a of the layer 12 to form the source 17 of the bipolar field-effect transistor. Ohmic contacts are made to the section 14 `and to the block 11 on the yside opposite the layer 12, which contacts rare connected together to form an electrode 19 of the bipolar field-effect transistor. The electrode 119 in the bipolar iield-eect transistor is structurally the same as the gate 19 in the unipolar held-effect transistor. In the Ibipolar iield-eiect transistor, however, this electrode is referred to as the collector. As can be seen in FIG- URE 2, the bipolar iield-eiTec-t transistor differs from the unipolar iield-eect transistor in that `a `diiiused section 20 of N-type material is provided in the part 12b of the layer 12 of Pmtype material. This section Zti of N-type material extends down into the layer '12. of P-type material not quite as far yas the junction 13. An olhrnic contact is made to the section 2t? forming the emitter 21 of the bipolar iield-etfect transistor. The section 2? forms a PN junction 22 with the P-type material of the layer 12. The PN junctions 20 and 13 will coact to provide junction transistor action and, .as a result, the bipolar field-effect transistor will function as ya junction transistor and unipolar lield-eiect transistor connected together in a circuit, Which is shown in FiGURE 3.

FlfURES 2b and 2c show a particular physical embodiment of the bipolar iield-eiect transistor of FIGURE 2a which has been found to be especially desirable. A specific example of a method of producing this structure will now be described. A wafer 116 of silicon of a resistivity of 7.5 ohm-centimeters is used as the starting material. Each side of the wafer is lapped to achieve wafer thickness of l0 mils. The upper side of the wafer is then optically polished. After the polishing operation, the Wafer is placed in an open tube, and steam of a temperature of approximately 1200" C. is allowed to pass over the wafer. This' operation causes a thin oxide film to form on all surfaces of the wafer. The wafer is then subjected to diifusion from a gallium trioxide source in the presence of dry oxygen to form a layer of P-type material approximately 0.7 mil thick in the surface of the wafer. Using photoresist techniques, the oxide lm is then selectively removed from concentric circular portions of the wafer surface. After the selective removal of the oxide iilm, the wafer is subjected to a second diffusion cycle in which phosphorous is diiIused to a depth of approximately 0.3 mil from a phosphorous pentoxide source in the presence of dry nitrogen. The resulting thin layer of P-type material is then removed from the bottom and sides of the water, leaving a layer 112 of P-type material on the surface of the wafer which makes a PN junction 125 with the N-type material of the wafer. The second step of diffusion from the source of phosphorous pentoxide causes concentric circular sections 114 and 116 of N-type material to be formed in the layer 12 making PN junctions with the P-type material of the layer 12. Ohmic contacts 120 and 122 to the sections 116 and 114i, respectively, are provided. An ohmic contact 121i to the layer 112 is provided at the center about which the circular sections 114 and 116 are positioned. An ohmic contact 113 is provided to the bottom of the wafer 110. The contacts 118, 120, 122, and 124 are of aluminum, and are formed by evaporation and sintering terchniques. The wafer is then masked with an etchresistant material such as Wax, and the wafer etched in an acid solution to achieve the mesa conguration shown in FIGURE 2c.

The resulting device is a bipolar field-effect transistor which is equivalent to the device in FIGURE 2a. In the device in FIGURES 2b and 2c, the contacts 124 and 12) correspond to the source 17 and the emitter 21, respectively, in FEGURE 2a. The contacts 122 and 118 in FIGURES 2b and 2c will be connected together and correspond to the collector 19 in FIGURE 2a. The sections 114 and 116 in FIGURES 2b and 2c correspond to the sections 14 and 20, respectively, in FIGURE 2a.

It is to be noted that, in some instances, it may be desirable that the sections 114 and 116 be diffused to diiterent depths or have different impurity concentrations therein. In such instances, it will be necessary to form the sections by different diiusion cycles. In the preterred embodiment, however, only one ditusion cycle is used to form both sections 114 and 116.

The circuit in FIGURE 3 is the equivalent circuit of the bipolar held-effect transistor. As shown in FIGURE 3, the equivalent circuit comprises a unipolar held-effect transistor 23 and a junction transistor 25, which in the specific embodiment of the present invention is an NPN transistor. In FIGURE 3, the source of the unipolar iieldefect transistor 23 is designated by the reference number 26, the gate by the reference number 28, and the drain by the reference number 27. The unipolar held-effect transistor 23 has its drain connected directly to the base of the junction transistor 2S. The gate of the field-eiiect transistor 23 is connected directly to the collector of the junction transistor 25. The source of the bipolar eldeffect transistor corresponds in its equivalent circuit to the source 26 of the unipolar held-effect transistor 23. The collector of the bipolar held-effect transistor corresponds in its equivalent circuit to the common connection between the gate 23 of the unipolar held-effect transistor 23 and the collector of the junction transistor 25. The emitter of the bipolar held-effect transistor corresponds in its equivalent circuit to the emitter of the junction transistor 2S.

A collector voltage versus collector current characteristic for the bipolar field-effect transistor and for its equivaient circuit is shown in FIGURE 4. This characteristic is for a constant source voltage of 1.7 volts. This characteristic, as seen in FIGURE 4, has a positive resistance portion 31 and a negative resistance portion 32. The negative resistance portion of the characteristic arises when the junction transistor 25 is not in saturation. As the collector voltage rises, the voltage applied to the gate of the unipolar field-effect transistor 23 will rise, and this will decrease the drain current owing from the field-effect transistor 23. In this manner, the base current flowing to the junction transistor 25 is decreased, and this decrease in base current will cause a decrease in the collector current. Thus, as the collector voltage is increased, the col- 7 lector current of the transistor 2S will decrease, thus providing the negative resistance portion of the characteristic. The positive resistance portion of the characteristic occurs during the time that the junction transistor ZS is saturated. At low values of collector voltage, the drain current of the held-effect transistor 23 will be high, and thus the base current of the transistor 25 will be high enough to cause the transistor 25 to saturate. As the collector voltage is increased, it will decrease the current flowing from the drain of the field-eiect transistor 23. However, since the transistor 25 is in saturation, this will have no effect on the collector current of the transistor 25. Therefore, the collector current will increase as the collector voltage increases, thus providing the positive resistance portion 31 of the characteristic shown in FIG- URE 4. The point at which the characteristic changes from positive resistance to negative resistance is the point at which transistor 25 comes out of saturation.

From FIGURE 4, it will be seen that the device has bistable properties. For example, the 1500 ohm load line 34, drawn from the point represented by 5 milliamperes and Zero volts to the point represented by zero milliamperes and 7.5 volts, crosses the characteristic three times. One crossing is on the positive resistance portion 31 of the characteristic, another crossing is on the negative resistance portion 32, and the third crossing is on the cut-oli line at a current of zero milliamperes. Therefore, two stable points are provided, one being on the positive resistance portion where the transistor 25 is in saturation, and the other being on the cut-off line where the fieldeffect transistor 23 is pinched off and the junction transistor 25 is cut oif.

FIGURE 5 exemplies the switching characteristics of the device. In FIGURE 5, the reference number 35' generally designates the bipolar eld-elect transistor, in order to facilitate the description of the operation of the device, which is represented by its equivalent circuit comprising che unipolair field-effect transistor Z3 and the junction transistor 25. In FIGURE 5, the emitter 21 of the bipolar eld-eect transistor 35 is grounded and the collector 19* is connected to a source of positive voltage through a 300 ohm resistor 36. The source 17 of the bipolar field-effect transistor 35 is connected to the positive terminal of a variable voltage source 38 through the series circu-it of a 2 kilohm resistor 40 and a 51 ohm resistor 42. The negative terminal of .the source 33 is grounded. A terminal @4 is connected to the junction between resistors it? and i2 to provide an input to the circuit.

If the circuit is in the condition in which the held-effect transistor is pinched ott and the junction transistor is cut o, and a positive pulse is applied to the input 44, the voltage at the source 17 will rise at a rate depending on the #RC time constant associated with the input resistor 40 and the capacitance from the source 17 to ground. When the voltage at the source 17 starts to rise, the gate-tosource voltage of the field-effect transistor 213 will decrease. When this gate-to-source voltage decreases to a value below the pinch-off voltage lfor the ield-etect transistor 23, the field-effect transistor 23 will start to conduct. When the tield-eiect transistor starts to conduct, it will supply current to the base of `the junction transistor 25. The base current owing in the junction transistor 2S will start collector current to tlow in the junction transisto: 2S and the collector voltage of the junction transistor 2S will drop. As a result, the Voltage at the gate or the field-effect transistor Z3 drops, and more current flows through the held-effect transistor 26. The action is regenerative, and the ield-elect transistor and the junction transistor are switched quickly to a fully conducting condition. If the ield-eiect transistor supplies enough current to the base of the junction transistor, it will saturate, the diode from the gate-to-source of the field-effect transistor 2'3 will become lforward-biased, and the voltage at the source 17 will be clamped to the voltage at the collector 19. The device will remain fully conducting until the voltage at the source 17 is :decreased to less than the voltage at the collector 19, at which time the iield-eilect transistor Z3 will start to be pinched olf. A regenerative action will come into play to switch the device to a nonconducting condition if the junction transistor acts faster than the held-effect transistor 23. Otherwise, the fieldetect transistor will become n-onconducting while the junction transistor is still in storage.

It should be noted that, when the junction transistor 25 is saturated, the voltage from the collector to the base of the junction transistor 2S is about zero volts; therefore, the voltage -from the source to the drain of the held-effect transistor 23 will be the same approximately as the voitage from the sourec to the gate, and the held-effect transistor Z3 will be in its saturation region. Therefore, the source-to-drain current of the iield-edect transistor may be less than its limiting value. If the junction transistor 25 requires the limiting value of drain current as base current to saturate, it will never saturate, and the iieldeiect transistor 23 will act as a base current clamp to keep the junction transistor 25 out of saturation. O- course, the low-gain junction transistors are the ones that would not saturate. 'llhese low-gain devices would be the slowest switching to a fully conducting condition because there would be less loop gain, but they would be cut oi faster because of decreased storage time.

The loop gain and the RC circuit of the input resistance 4%- and the capacitance `from the source 17 to ground determine the rise time of the circuit. The storage and fall time or" the circuit depend almost entirely on the storage and `fall time of the junction transistor 215.

FIGURE 6 illustrates how the bipolar eld-eiect transistors are connected in the circuit -for the ring counter which comprises the present invention. In FIGURE 6, the bipolar ield-eiiect transistors are designated generally by the reference number 35, and, in order to facilitate description of the operation Iof the invention, -they are represented by the equivalent circuit shown in FGURE 3. Thus, eaoh bipolar field-effect transistor 3S is represented by unipolar tie'ld-ett'ect transistor 26 and a junction tra sistor 2-5 with the drain ot the unipolar field-effect transistor 2:3` connected directly to the base of the junction transistor 25 and with the gate of the unipolar ield-etect transistor 2-3 connected directly to the collector of the junction transistor 2.5. The connection between the gate of unipolar eld-eect transistor 23 and the collector of junction transistor E5 provides the collector 19 for the bipolar field-effect transistor; the source of the unipolar eldeect transistor 23 provides the source 17 olf the bipolar fiefld-etiect transistor; and the emitter' of the junction transistor 25 provides the emitter 21 of the bipolar iield-eie-ct transistor.

The ring counter comprises a plurality of identical stages which may be of any nurnber. In the specitic embodiment of the present invention, only four stages are shown to simpiify the showing in the drawings. These are designated generally by the reference numbers 41, 42, 43, and 44. Each stage of the ring counter comprises a bipolar fleld-eiect transistor 35 which has its collector connected Itl'zrough a 3G() ohm resistor 47 to a source of +1() volts common to all three stages applied at a terminal 49'. In each stage of the ring counter, the emitter 21 is connected through a 209 ohm resistor S1 to ground. In each stage of the ring counter, a capacitor 53 connects the source 17 of the bipolar held-effect transistor 3S to an input S5 common to all three stages. The input 55 is connected to ground by 5l ohm resistor 57. The collector 19 in each stage is connected through a 1.5 kilohrn resisto-r 59 to the source 17 of the next preceding stage. Thus, a resistor 59 connects the source 17 of the stage 41 to the collector 19 in the stage 4Z; a resistor Si) connects the source 17 in the stage 4Z to the collector 19 in the stage 43; a resistor 59 connects the source 17 in the stage 43 to the collector 19 in the stage 44; and a resistor 59 connects the source 17 in the stage 44 to the collector 19 in the stage 41. Similarly, a 2.2. kilohm resistor 61 in each stage connects the source 17 tothe emitter 211 in the preceding stage. Thus, the resistor 6d. in the stage 44 connects the source 17 of this stage to the emitter Z1 in the stage 43; the resistor 61 in the stage 413 connects the source 17 in this stage to the emitter 21 in the stage 42; the resistor 61 in the stage 42 connects the source 17 in this stage to the emitter 21 in the stage 41; and the resistor 61 in the stage 41 connects the source 17 in this stage tothe emitter 21 in the stage 44.

Each of the stages 41, 42, 43, and `44 have two stable states. One stable state will be with the transistor 2S conducting and the eld-eiect transistor 23 conducting. In this condition, the stage is referred to as being turned on. In the other stable state, the feld-eiiect transistor 23 will be pinched oit, and Kas a result, the junction transistor 25 will be cut orf. In this stable state, the stage shall be referred to as being turned ott. It shall be assumed for purposes of description that the stage 41 is turned on, and that the stages 42, 43, and 44 are turned oli. In. the stages which are turned oft, the collectors 19 will be substantially at +10 volts. Similarly, the emitters of the stages which are turned `oit will be substantially at zero volts. The voltage at the sources 17 in each ot the turnedoit stages 42, 43, and 44 is determined by the voltagedividing effect of the resistors 61 and 59. Thus, the Voltage at each source 17 in the turned-oli stages will be sixtenths `of the difference between the voltage 1at the oollector of the succeeding stage and the voltage at the emit-ter -of the preceding stage. For example, the voltage at the emitter 21 of the stage 42 is zero volts, and the voltage at the collector 19 of the stage 44 is +10 volts. Thus, the voltage applied to the source 17 -of the stage 43 will be six-tenths of +10 volts, or +6 volts. Since the voltage applied to the collector 19 of the stage 43 is +410 volts, the gate-to-source voltage oi the iield-etleot transistor 23 will be +4 volts, which is suiiioient to maintain iield-eieot transistor pinched-oit", and in this manner, the stage 43 is maintained in its turned-oit stable state. Since the stage 41 is turned on, the voltage at the collector 1910i the stage 41 will be considerably less than +10 volts due to the Voltage drop through the resistor 47. As a result, the volt-age applied to the source 17 of the stage 44 will even be less than +6 volts, and the gate-to-source voltage of the field-effect transistor 23 in the stage 44 will be even greater than +4 volts. Therefore, the stage 44 will also be maintained in its turned-oil stable state. Since rthe stage 41 is turned on, the voltage at the emiter 21 of this stage will be considerably greater than zero, and thus the voltage applied at the source 17 of the stage 42 ywill be greater Ithan l+6y volts. The values of the resistors 59 and 61 are selected so that the voltage applied to the source 17 doe-s not rnake the gate-to-source voltage of the field-effect transistor 23 in the stage 42 less than the pinch-oft" voltage. Thus, the field-effect transistor 23 will be maintained pinched-ofi, and the stage 42 will be main-tained in its turned-oit stable state. It will be noted, however, that the gate-to-source voltage of the field-effect transistor 23 in the lstage 42 will be less than the gate-to-source volt-age of the iield-etlect transistors 213 1n the stages 43 and 44. The values of the resistorsr 59 and 61 are selected so that the gate-to-source voltage in the field-effect transistor 23 in the stage 42 is just greater than the pinch-off voltage for reasons which will be explained below. Since the field-effect transistor 23 in the stage 41 is conducting, fthe voltage applied to the source 17 of this stage will be consider-ably less than the +6 volts, since a large amount of the current ilowing through the resistor 59 will iow into the source of the field-effect transistor 23. As pointed vout above, `since the stage 41 is conducting, there will be a large voltage drop through the resistor `47. rthis voltage drop will be suflicient to bring the voltage between the collector 19 and the source 17 in the stage considerably less than the pinch-oli Voltage of the held-effect transistor 23. The iield-cliect transistor 23 will ltherefore be maintained conducting, and the stage 41 will be maintained in its turned-on stable state.

When `an input pulse is applied to the terminal 55, it will be applied through the capacitors 53 to the sources 17 in each stage. This will have the elect of raising the vol-tage at the source 17 in each stage and decreasing the gate-to-source voltage in each stage. Since the stage 41 is already turned on, it will not have any elect on this stage. This voltages at the sources 17 in the stages i3 `and de will be sufliciently low that the input pulse will not raise the potential at the sources 17 in the stages 43 and 4d enough to bring the gate-to-source voltage of the lieldeiect transistors 23 in .these stages below the pinched voltage. Therefore, the input pulse will not affect the stages 43 and 44. As pointed out above, the potential at the source 17 in the stage 4Z, however, is just above the pinch-off voltage, and when Ithe input pulse is applied through the capacitor 53 to the source 17 in the stage 42, it will cause the voltage .at the source 17 in this stage to rise suiiiciently to bring the gate-to-source voltage of the field-effect transistor 23 in the stage 42 below the pinch-off vol-tage, and the held-effect transistor 23 in this stage will begin to conduct. When Iche held-effect tr-ansistor 23 in the stage 2 begins to conduct, it will cause current to iiow into the base of the junction transistor 25 in this stage and, thus, the junction transistor Z in stage 52; will begin to conduct. Current will start to iiow through the resistor 47 in the stage 42, and this will cause the voltage at the collector 19' in the stage 42 to drop. This drop in voltage at the collector 19 further decreases the gate-to-source vol-tage of the iield-etect transistor 23 in this stage, and thus more current tlows through the field-etiect transistor 23, allowing more current to :flow into the base of 4the transistor 2,5. The eiiect is regenerative, and the ield-eiect transistor 23 and the junction transistor 25 will become fully conducting. ln this manner, the stage 42 is turned on. The drop in voltage at the collector 19 is transmitted rto the source 17 in the stage 42 by means of the resistor 59. When the voltage at the source 17 in the stage 41 drops, the gate-to-source voltage of the held-effect transistor 23 in the stage 41 increases. This increase in the gate-tosource voltage of the -ield-efiect transistor 23 in this stage reduces the current flowing through this field-effect transistor, and thus reduces the current flowing through the junction transistor 25. This causes a rise in the potential at the collector 19 in the stage vfil, and thus the gate-to-source potential of the `field-effect transistor 23 in the stage 41 is further increased. Therefore, the current Iflowing through the held-effect transistor decreases further. The action in the stage 41 is regenerative, land the stage is turned oit, Thus, `after the pulse has been applied -to the input 55, the stage 42. will be the stage which is turned on, and the stages 41, 43, and 44 will be turned off. Since each stage is identical and is connected with its adjacent stages in exactly the same manner, the stages 41, 43, and 44 will be maintained turned o in exactly the same manner that the stages 42, 43, and 44, respectively, were maintained turned olf when the stage 41 4was conducting. Similarly', v,the stage 42 lwill be maintained turned `on in the same manner that the strage 41 was maintained turned on. The next pulse applied to the input 55 will cause the stage 43 to turn on which, in turn, lwill cause the stage 42 to 'turn `oit in the same manner that the stage 42 was turned 'on and the stage 41 was turned off. -Each succeeding jpulse will cause each succeeding stage to turn on, and the preceding stage to itu-rn, off in the same manner. The next pulse applied after the stage 44 has been turned on will cause the stage 41 to turn on again, and the stage 44 will be turned oft. The device will operate in this manner continuously as long `as pulses are applied to the input 55.

The principles of the present invention will also provide a dip-Hop. This flip-nop circuit is provided when the Ting Counter is built as just two stages. When the ring counter is connected in two stages as a ilip-iiop circuit, larger input pulses will be required to cause switching because the source 17 in the stage which is turned oft will be ata lower voltage due to its connection to the collector lof the stage which is turned on .through the resistor 59 of the stage which is turned on.

FIGURES 7 and 8 illustrate the embodiment of the ring counter in solid-state networks. A solid-statenet- Work is provided for each stage of the ring counter. Since each stage of fthe ring counter is identical, each solid-state network providing the circuitry for each stage will be identical. FEGURES 7 and 8 illustrate the solidstate network for one of the stages of the ring counter. As shown in these figures, the solid-state network comprises an oblong block of N-type material 71 on which there is diffused a layer of P-type material. At one end of the oblong block, a slot 73 is cut through the layer of P-type material, dividing i-t into two pants 75 and 77, the part 75 being much longer Ialong the oblong block 7d than the part 77. A section 79 of N-type material is formed by diffusion in the layer of P-type material at one end of the part 75. A second section 81 if N`type material is formed by ditusion in the Ptype layer close to the section 79, leaving la short path of P-type material join-ing the two sections 79 and 81. The sections 79 yand 81 are diffused to a depth not quite as far as the P-N junction between the N-type material of block 71 and the P-type material of pant 75. Evaporated aluminum contacts 83 and 3S are formed on the part 77 of the P-type layer at opposite sides thereof. An evaporated aluminum contact 87 is formed on the section 79 of N-type material. An evaporated aluminum contact S9 is formed on the section S1 of N-type material. An evaporated aluminum contact 91 is -formed on the part 75 of the P-type layer close to the section 81 and on the opposite side thereof from the section 79, A second evaporated aluminurn contact 161 is also formed on part 75 of the P-type layer at the opposite end from `the sections 79 and S1. The aluminum contacts 83, 8S, 91, and 131 make `ohrnic contact with the layer of P-type material and the contacts 37 and 89 make ohmic contact with the sections of 79 and v81, respectively. Olmric contacts in the form of tabs 1%, 105, and 157 are formed on the block of N-type material on the opposite side from the layer of P-type material made up of the parts 75 and 77. The ohmic contact 193 is formed directly below the part 77 of the P-type layer. The ohmic contact is formed directly below the section 79 of N- type material and the ohmic contact 11i? is formed at the opposite end of the block 71 of N-type material beneath the aluminum contact 101. The semiconductor network shown in FIGURES 7 and 8 can be fabricated by the same techniques described for the fabrication of the bipol-ar field-effect transistor shown in FIGURES 2b and 2c.

The above-described device shown in FIGURES 7 and 8 Ican be used to provide almost the entire circuitry for a single stage of the ring counter. In order to use this device for the circuitry of a single stage, the Contact 85 must be connected directly to the Contact 87 and the contact 39 must be connected directly to the contact 195. The capacitor 53 of each stage is not provided in the solid-state network and must be connected externally. This capacitor will be connected to the contact 91. When this solid-state network is used in the ring counter, the contact S3 will be grounded `and -l-lO volts Will be applied to the terminal 103. With the block connected in this manner, the complete circuitry for a single stage of the ring counter is provided, The resistance of the conducting path through the par-t 77 of the P-type layer between the contacts 33 and 8S provides the resistance 51 for the stage. The resistance of the path through the part 75 of the P-type layer between the contacts 91 and lit-1 provides the resistor `61. The resistance of the path through the N-type semiconductor material of the block '71 between the contacts 165 and 167 provides the resistor 59. The resistance of the path between the contacts 193`and 165 through the N-type material of the block 7i. provides the resistor 47. The sections '79 and di, the PN junction between lthe layer of P-type material and the block '71 of N-type material beneath these sections, and the contacts 87, 89, 91, and 105 with the contacts S9' and 165 connected together provide the bipolar field-effect transistor, the contact 91 providing the source of the bipolar fieldeffcct transistor, the common connection to the contacts 89 and 105 providing the collector -of the bipolar transistor, and the contact 87 providing the emitter of the bipolar field-effect transistor.

Thus, to connect a plurality of these stages formed out of semiconductor networks, as disclosed in `FGURES 6 and 7, the contact 161i of each succeeding stage should be connected to the contact $7 of the preceding stage and the contact 91 of each preceding stage should be connected to the contact 107 of the succeeding stage. The unconnected terminals of the capacitors 53 connected to the contacts 91, of course, will be connected together to the input terminal 55 -and through the resistor 57 to ground, as shown in FIGURE `6. ln this manner, the ring counter is provided with solid-state networks.

The above description is of a preferred embodiment of the invention, and many modifications may be made thereto Without departing from the spirit and scope of the invention which is limited only as defined in the appended claims.

What is `claimed is:

1. In a ring counter circuit, a plurality of bipolar fieldeffect transistors, each of said transistors having source, collector and emitter electrodes, a voltage source having first and second terminals, said collector electrode in each of said transistors being connected through one of a plurality of resistors to said first terminal, said emitter electrode in each of said transistors being connected through one of another plurality of resistors to said second terminal, said source electrode in each of said transistors being connected through one of another plurality of resistors to said emitter electrode `in the next preceding one of said transistors, said source electrode in each of said transistors being further conected through one of another plurality of resistors to said collector electrode `in the next succeeding one of said transistors, and means for coupling input pulses to said source electrodes in each of said transistors.

2. In a ring counter circuit, a plurality of bipolar fieldeifect transistors, each of said transistors having source, collector and emitter electrodes, voltage supply means having terminal means of opposite polarities, said collector electrode in each of said transistors being D.C. coupled through resistance means to said terminal means of one polarity, said emitter electrode in each said transistor being D.C. coupled through resistance means to said means of the other polarity, said source electrode in each of said transistors being D.C. coupled through resistance means -to said emitted electrode in the next preceding one of said transistors, said source electrode in each of said transistors being further D.C. coupled through resistance -means to said collector electrode in the next succeeding one of said transistors, and means for coupling input pulses to said source electrodes in each of said transistors.

3. in a ring counter circuit, a plurality of bipolar fieldeffect transistors, each of said transistors having source, collector and emitter electrodes, voltage supply means having first and second terminals, said collector electrode in each of said transistors being D.C. coupled through resistance means to said yfirst terminal, said emitter electrode -in each of said transistors being D.C. coupled through resistance means to said second terminal, said source electrode in each of said transistors being D C. coupled through resistance means to said emitter electrode in the next preceding one of said transistors, said source electrode in each of said transistors being further D.C. coupled through resistance means to said collector electrode inthe next succeeding one of said transistor-s.

4. In a ring-counter circuit, a plurality of semiconductor devices comprising wafers of monocrystalline semiconductor material, a first region of one conductivity-type define-d in each of said wafers, a second region of opposite conductivity-type defined in each of said wafers contiguous to said first region and adjacent the surface thereof, a third region and a fourth region of said one conductivitytype defined in each of said wafers contiguous to said second region and adjacent the surface thereof, said third and fourth regions being spaced from said rst region and from one another, a portion of said second region in each of said wafers being connected within said wafer to said fourth region only by a thin channel of said second region underlying said third region, said first and third regions in each of said devices being electrically `connected together, a voltage source having lfirst and second terminals, said first region in each of said devices being connected through one of a plurality of resistors to said first terminal, said fourth region in each of said devices being connected through one of another plurality of resistors to said second terminal, said portion of said second region in each of said devices being connected through one of another plurality of resistors to said fourth region in the next preceding one of said devices and being further connected through one of another plurality of resistors to said first region `in the next succeeding one of said devices, and means for coupling input pulses to said portion of said second region in each of said devices whereby ring-counter operation -is provided.

5. -In a ring-counter circuit, a plurality of semiconductor devices comprising wafers of monocrystalline semiconductor material, a `first region of one conductivity-type defined in each of said wafers, a second region of opposite conductivity-type defined in each of said wafers contiguous to said first region and adjacent the surface thereof, a third region and ya fourth region of said one conductivitytype defined in each of sai-d wafers contiguous to said second region and adjacent the lsurface thereof, said third and fourth regions being spaced from said `first region and from one another, a portion of said second region in each of said wafers being connected within said Wafer to said fourth region only by a thin channel of said second region underlying said third region, said first and third regions in each of said devices being electrically connected together, voltage supply means having terminal means of opposite polarity, said 'first region -in each of said devices being D.C. coupled through resistance means to said terminal means of one polarity, said fourth region in each of said devices being D.C. coupled through resistance means to said terminal means of the opposite polarity, said portion of said second region in each of said devi-ces being D.C. coupled through resistance means to said fourth region in the next preceding one of said devices and being further D.C. coupled through resistance means to said fir-st region in the next succeeding one of said devices.

References Cited in the le of this patent UNITED STATES PATENTS Odell et al. July 5, 1960 OTHER REFERENCES 

3. IN A RING COUNTER CIRCUIT, A PLURALITY OF BIPOLAR FIELDEFFECT TRANSISTORS, EACH OF SAID TRANSISTORS HAVING SOURCE, COLLECTOR AND EMITTER ELECTRODES, VOLTAGE SUPPLY MEANS HAVING FIRST AND SECOND TERMINALS, SAID COLLECTOR ELECTRODE IN EACH OF SAID TRANSISTORS BEING D.C. COUPLED THROUGH RESISTANCE MEANS TO SAID FIRST TERMINAL, SAID EMITTER ELECTRODE IN EACH OF SAID TRANSISTORS BEING D.C. COUPLED THROUGH RESISTANCE MEANS TO SAID SECOND TERMINAL, SAID SOURCE ELECTRODE IN EACH OF SAID TRANSISTORS BEING D.C. COUPLED THROUGH RESISTANCE MEANS TO SAID EMITTER ELECTRODE IN THE NEXT PRECEDING ONE OF SAID TRANSISTORS, SAID SOURCE ELECTRODE IN EACH OF SAID TRANSISTORS BEING FURTHER D.C. COUPLED THROUGH RESISTANCE MEANS TO SAID COLLECTOR ELECTRODE IN THE NEXT SUCCEEDING ONE OF SAID TRANSISTORS. 